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Chromium toxicity refers to any poisonous toxic effect in an organism or cell that results from exposure to specific forms of chromium—especially hexavalent chromium. [1] Hexavalent chromium and its compounds are toxic when inhaled or ingested. Trivalent chromium is a trace mineral that is essential to human nutrition.
Many metals, particularly heavy metals are toxic, but some are essential, and some, such as bismuth, have a low toxicity. Metals in an oxidation state abnormal to the body may also become toxic: chromium(III) is an essential trace element, but chromium(VI) is a carcinogen. Only soluble metal-containing compounds are toxic.
Chromium, especially hexavalent chromium, is highly toxic to fish because it is easily absorbed across the gills, readily enters blood circulation, crosses cell membranes and bioconcentrates up the food chain. In contrast, the toxicity of trivalent chromium is very low, attributed to poor membrane permeability and little biomagnification. [141]
Hexavalent chromium (chromium(VI), Cr(VI), chromium 6) is any chemical compound that contains the element chromium in the +6 oxidation state (thus hexavalent). [1] It has been identified as carcinogenic, which is of concern since approximately 136,000 tonnes (150,000 tons) of hexavalent chromium were produced in 1985. [ 2 ]
A 2007 toxicity report for the National Toxicology Program provided evidence that high doses of chromium 6 caused cancers of the gastrointestinal tract in rats and mice at levels higher than 5 mg/L of water, (5 ppm, or 5,000 ppb). [41] [42] Average hexavalent chromium levels in Hinkley were recorded at 1.19 ppb, with an estimated peak of 20 ppb.
Chromium supplementation in general is subject to a certain amount of controversy as it is by no means clear that chromium is an essential element in human biology. [25] Nevertheless, chromium is an ingredient in total parenteral nutrition, along with other trace minerals. [26] It is also in nutritional products for preterm infants. [27]
The river water was contaminated with toxic metals including arsenic, copper, barium, cadmium, chromium, lead, mercury, nickel, and thallium. [2] Cleanup costs may exceed $1.2 billion. [3] A toxic heavy metal is a common but misleading term for a metal-like element noted for its potential toxicity. [4]
Chromium usage can be seen in, "industries such as metallurgy, electroplating, production of paints and pigments, tanning, wood preservation, chemical production and pulp and paper production." [ 19 ] Chromium toxicity affects the "biological processes in various plants such as maize, wheat, barley, cauliflower, citrullus and in vegetables.